Benzidine derivative, method for producing benzidine derivative, and electrophotographic photosensitive member

ABSTRACT

A benzidine derivative is represented by general formula (1). In the general formula (1), R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , and R 10  each represent, independently of one another, a hydrogen atom, a halogen atom, an optionally substituted alkyl group having a carbon number of at least 1 and no greater than 6, an optionally substituted alkoxy group having a carbon number of at least 1 and no greater than 6, or an optionally substituted aryl group having a carbon number of at least 6 and no greater than 14. n represents an integer of at least 0 and no greater than 2.

INCORPORATION BY REFERENCE

The present application claims priority under 35 U.S.C. §119 to JapanesePatent Application No. 2015-149468, filed on Jul. 29, 2015. The contentsof this application are incorporated herein by reference in theirentirety.

BACKGROUND

The present disclosure relates to a benzidine derivative, a method forproducing a benzidine derivative, and an electrophotographicphotosensitive member.

The electrophotographic photosensitive member is used in anelectrophotographic image forming apparatus. The electrophotographicphotosensitive member includes a photosensitive layer. Theelectrophotographic photosensitive member is for example a multi-layerelectrophotographic photosensitive member or a single-layerelectrophotographic photosensitive member. The multi-layerelectrophotographic photosensitive member includes, as thephotosensitive layer, a charge generating layer having a chargegenerating function and a charge transport layer having a chargetransport function. The single-layer electrophotographic photosensitivemember includes, as the photosensitive layer, a single-layer typephotosensitive layer having a charge generation function and a chargetransport function.

An example of the electrophotographic photosensitive member has aphotosensitive layer containing an arylamine-based compound. An exampleof the arylamine-based compound is represented by chemical formula(HT-B).

SUMMARY

A benzidine derivative according to an aspect of the present disclosureis represented by general formula (1) shown below.

In the general formula (1), R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, and R₁₀each represent, independently of one another, a hydrogen atom, a halogenatom, an optionally substituted alkyl group having a carbon number of atleast 1 and no greater than 6, an optionally substituted alkoxy grouphaving a carbon number of at least 1 and no greater than 6, or anoptionally substituted aryl group having a carbon number of at least 6and no greater than 14, and n represents an integer of at least 0 and nogreater than 2.

A method for producing a benzidine derivative according to anotheraspect of the present disclosure is a method for producing theabove-described benzidine derivative. The method for producing thebenzidine derivative according to the aspect of the present disclosureincludes performing a reaction represented by scheme (R-6) shown below.

In the scheme (R-6), R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, and R₁₀ eachrepresent, independently of one another, a hydrogen atom, a halogenatom, an optionally substituted alkyl group having a carbon number of atleast 1 and no greater than 6, an optionally substituted alkoxy grouphaving a carbon number of at least 1 and no greater than 6, or anoptionally substituted aryl group having a carbon number of at least 6and no greater than 14. n represents an integer of at least 0 and nogreater than 2. X represents a halogen atom.

An electrophotographic photosensitive member according to another aspectof the present disclosure includes a conductive substrate and aphotosensitive layer. The photosensitive layer contains at least acharge generating material and the above-described benzidine derivativeas a hole transport material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a ¹H-NMR spectrum for a benzidine derivative represented bychemical formula (HT-2) according to an embodiment of the presentdisclosure.

FIG. 2 is a ¹H-NMR spectrum for a benzidine derivative represented bychemical formula (HT-3) according to the embodiment of the presentdisclosure.

FIGS. 3A, 3B, and 3C are schematic cross sectional views eachillustrating an example of an electrophotographic photosensitive membercontaining a benzidine derivative according to the embodiment of thepresent disclosure.

FIGS. 4A, 4B, and 4C are schematic cross sectional views eachillustrating another example of the electrophotographic photosensitivemember containing a benzidine derivative according to the embodiment ofthe present disclosure.

DETAILED DESCRIPTION

The following describes an embodiment of the present disclosure indetail. However, the present disclosure is not in any way limited by theembodiment described below. Appropriate variations may be made inpracticing the present disclosure within the intended scope of thepresent disclosure. Although description is omitted as appropriate insome instances in order to avoid repetition, such omission does notlimit the essence of the present disclosure.

Hereinafter, the term “-based” may be appended to the name of a chemicalcompound in order to form a generic name encompassing both the chemicalcompound itself and derivatives thereof. Also, when the term “-based” isappended to the name of a chemical compound used in the name of apolymer, the term indicates that a repeating unit of the polymeroriginates from the chemical compound or a derivative thereof. Compoundsrepresented by general formulae or chemical formulae (2) to (11), (2a),(3a), (5a), (6a) to (6c), (7a) to (7c), (8a) to (8c), (9a) to (9e),(10a), and (11a) to (11c) may be respectively referred to as compounds 2to 11, 2a, 3a, 5a, 6a to 6c, 7a to 7c, 8a to 8c, 9a to 9e, 10a, and 11ato 11c.

Hereinafter, unless otherwise stated, a halogen atom, an alkyl grouphaving a carbon number of at least 1 and no greater than 6, an alkoxygroup having a carbon number of at least 1 and no greater than 6, and anaryl group having a carbon number of at least 6 and no greater than 14each mean the following.

A halogen atom as used herein is for example fluorine (fluoro group),chlorine (chloro group), or bromine (bromo group).

An alkyl group having a carbon number of at least 1 and no greater than6 as used herein refers to an unsubstituted straight chain or branchedchain alkyl group having a carbon number of at least 1 and no greaterthan 6. Examples of the alkyl group having a carbon number of at least 1and no greater than 6 include a methyl group, an ethyl group, a propylgroup, an isopropyl group, an n-butyl group, an s-butyl group, a t-butylgroup, a pentyl group, an isopentyl group, a neopentyl group, and ahexyl group.

An alkoxy group having a carbon number of at least 1 and no greater than6 as used herein refers to an unsubstituted straight chain or branchedchain alkoxy group having a carbon number of at least 1 and no greaterthan 6. Examples of the alkoxy group having a carbon number of at least1 and no greater than 6 include a methoxy group, an ethoxy group, ann-propoxy group, an isopropoxy group, an n-butoxy group, an s-butoxygroup, a t-butoxy group, a pentyloxy group, an isopentyloxy group, aneopentyloxy group, and a hexyloxy group.

An aryl group having a carbon number of at least 6 and no greater than14 as used herein is for example an unsubstituted monocyclic aromatichydrocarbon group having a carbon number of at least 6 and no greaterthan 14, an unsubstituted fused bicyclic aromatic hydrocarbon grouphaving a carbon number of at least 6 and no greater than 14, or anunsubstituted fused tricyclic aromatic hydrocarbon group having a carbonnumber of at least 6 and no greater than 14. Examples of the aryl grouphaving a carbon number of at least 6 and no greater than 14 include aphenyl group, a naphthyl group, an anthryl group, and a phenanthrylgroup.

[Benzidine Derivative]

An embodiment of the present disclosure is directed to a benzidinederivative. The benzidine derivative according to the present embodimentis represented by general formula (1) shown below.

In the general formula (1), R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, and R₁₀each represent, independently of one another, a hydrogen atom, a halogenatom, an optionally substituted alkyl group having a carbon number of atleast 1 and no greater than 6, an optionally substituted alkoxy grouphaving a carbon number of at least 1 and no greater than 6, or anoptionally substituted aryl group having a carbon number of at least 6and no greater than 14. n represents an integer of at least 0 and nogreater than 2.

The benzidine derivative represented by the general formula (1)(hereinafter, may be referred to as a benzidine derivative 1), whencontained in a photosensitive layer of an electrophotographicphotosensitive member (hereinafter, may be referred to simply as aphotosensitive member), can inhibit crystallization in thephotosensitive layer and improve electrical properties of thephotosensitive member. Presumably, the reason therefore is as follows.

The benzidine derivative 1 has two nitrogen atoms. A phenyl group havingR₁ to R₅ (short-chain conjugated group) and a group including a phenylgroup having R₆ to R₁₀ (long-chain conjugated group) are bonded to eachof the nitrogen atoms. It is thought that the benzidine derivative 1having such a structure has the following advantages.

A first advantage is that the benzidine derivative 1 has an asymmetricstructure as having the long-chain conjugated groups and the short-chainconjugated groups. Consequently, the benzidine derivative 1 is readilydissolved in a solvent that is used for photosensitive layer formation.Furthermore, the benzidine derivative 1 tends to be readily entangledwith the chain structure of a binder resin as a result of the benzidinederivative 1 having the movable long-chain conjugated groups. It istherefore thought that compatibility between the benzidine derivative 1and the binder resin is increased. Furthermore, the benzidine derivative1 tends to form a stacking structure having an interplanar distanceadjusted to a suitable distance as a result of the benzidine derivative1 having the long-chain conjugated groups. For the reasons state above,it is thought that a photosensitive layer containing the benzidinederivative 1 tends not to experience crystallization.

A second advantage is that the benzidine derivative 1 has a moderatelylarge molecular structure as having the long-chain conjugated groups.Consequently, a distance (hopping distance) between the π electron cloudof a molecule of the benzidine derivative 1 and the π electron cloud ofanother adjacent molecule of the benzidine derivative 1 that are presentin the photosensitive layer tends to be small. It is thought that as aresult, hole mobility between molecules of the benzidine derivative 1 isimproved, and thus electrical properties of the photosensitive member isimproved.

The alkyl group having a carbon number of at least 1 and no greater than6 that is represented by R₁ to R₁₀ in the general formula (1) ispreferably an alkyl group having a carbon number of at least 1 and nogreater than 3, and more preferably a methyl group or an ethyl group.The alkyl group having a carbon number of at least 1 and no greater than6 that is represented by R₁ to R₁₀ in the general formula (1) isoptionally substituted. The alkyl group having a carbon number of atleast 1 and no greater than 6 may for example have, as a substituent, ahalogen atom, an alkoxy group having a carbon number of at least 1 andno greater than 6, or an aryl group having a carbon number of at least 6and no greater than 14. The alkyl group having a carbon number of atleast 1 and no greater than 6 preferably has an aryl group having acarbon number of at least 6 and no greater than 14 as a substituent,more preferably an monocyclic aromatic hydrocarbon group having a carbonnumber of at least 6 and no greater than 14, and particularly preferablya phenyl group. Although no particular limitations are placed on thenumber of substituents, the alkyl group preferably has no greater thanthree substituents, and more preferably has one substituent.

The alkoxy group having a carbon number of at least 1 and no greaterthan 6 that is represented by R₁ to R₁₀ in the general formula (1) ispreferably an alkoxy group having a carbon number of at least 1 and nogreater than 3, and more preferably a methoxy group. The alkoxy grouphaving a carbon number of at least 1 and no greater than 6 that isrepresented by R₁ to R₁₀ in the general formula (1) is optionallysubstituted. The alkoxy group having a carbon number of at least 1 andno greater than 6 may for example have, as a substituent, a halogenatom, an alkoxy group having a carbon number of at least 1 and nogreater than 6, or an aryl group having a carbon number of at least 6and no greater than 14. Although no particular limitations are placed onthe number of substituents, the alkoxy group preferably has no greaterthan three substituents, and more preferably has one substituent.

The aryl group having a carbon number of at least 6 and no greater than14 that is represented by R₁ to R₁₀ in the general formula (1) ispreferably a monocyclic aromatic hydrocarbon group having a carbonnumber of at least 6 and no greater than 14, and more preferably aphenyl group. The aryl group having a carbon number of at least 6 and nogreater than 14 that is represented by R₁ to R₁₀ in the general formula(1) is optionally substituted. The aryl group having a carbon number ofat least 6 and no greater than 14 may for example have, as asubstituent, a halogen atom, an alkyl group having a carbon number of atleast 1 and no greater than 6, an alkoxy group having a carbon number ofat least 1 and no greater than 6, or an aryl group having a carbonnumber of at least 6 and no greater than 14. Although no particularlimitations are placed on the number of substituents, the aryl grouppreferably has no greater than three substituents, and more preferablyhas one substituent.

In the general formula (1), n represents an integer of at least 0 and nogreater than 2. Preferably, n represents 1 or 2. As a result of n being1 or 2, the benzidine derivative 1 has a moderately large molecularstructure, and the distance (hopping distance) between the π electroncloud of a molecule of the benzidine derivative 1 and the π electroncloud of another adjacent molecule of the benzidine derivative 1 thatare present in the photosensitive layer tends to be small. It is thoughtthat as a result, hole mobility between molecules of the benzidinederivatives 1 is improved, and thus electrical properties of thephotosensitive member is improved.

In order to improve electrical properties of the photosensitive member,R₆, R₇, R₈, R₉, and R₁₀ in the general formula (1) preferably eachrepresent a hydrogen atom.

In order to inhibit crystallization in the photosensitive layer andimprove electrical properties of the photosensitive member, R₁ to R₁₀ inthe general formula (1) preferably each represent as follows. R₁, R₂,R₃, R₄, and R₅ each represent, independently of one another, a hydrogenatom, an alkyl group having a carbon number of at least 1 and no greaterthan 6 and optionally having an aryl group having a carbon number of atleast 6 and no greater than 14, or an aryl group having a carbon numberof at least 6 and no greater than 14. R₆, R₇, R₈, R₉, and R₁₀ eachrepresent, independently of one another, a hydrogen atom or an alkoxygroup having a carbon number of at least 1 and no greater than 6. nrepresents 0 or 1.

Specific examples of the benzidine derivative 1 include benzidinederivatives represented by chemical formulae (HT-1) to (HT-6) shownbelow. Hereinafter, the benzidine derivatives represented by thechemical formulae (HT-1) to (HT-6) may be referred to as benzidinederivatives HT-1 to HT-6.

[Method for Producing Benzidine Derivative]

Preferably, a method for producing the benzidine derivative 1 includesperforming a reaction represented by scheme (R-6) shown below.Consequently, it is possible to readily produce the benzidine derivative1 that inhibits crystallization in the photosensitive layer and improveselectrical properties of the photosensitive member. The method forproducing the benzidine derivative 1 may involve, as necessary,reactions represented by schemes (R-1) to (R-5) shown below. Wherenecessary, alterations can be made to the reactions as appropriate.Hereinafter, the reactions represented by the schemes (R-1) to (R-6) maybe referred to as reactions R-1 to R-6.

In the schemes (R-1) to (R-6), R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀,and n are the same as defined for R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉,R₁₀, and n in the general formula (1). X represents a halogen atom.

(Reaction R-1)

In the reaction R-1, the compound 2 (1 equivalent) is caused to reactwith triethyl phosphite (1 equivalent) to give the compound 3 (1equivalent).

In the reaction R-1, at least one mole and no greater than 2.5 moles oftriethyl phosphite is preferably added relative to 1 mole of thecompound 2. If the number of moles of triethyl phosphite is too smallrelative to the number of moles of the compound 2, there may be areduction in the yield of the compound 3. On the other hand, if thenumber of moles of the triethyl phosphite is too large relative to thenumber of moles of the compound 2, purification of the compound 3 afterthe reaction may be difficult due to triethyl phosphite remainingunreacted.

The reaction temperature of the reaction R-1 is preferably at least 160°C. and no greater than 200° C., and the reaction time thereof ispreferably at least 2 hours and no greater than 10 hours.

(Reaction R-2)

In the reaction R-2, the compound 3 (1 equivalent) is caused to reactwith the compound 4 (1 equivalent) to give the compound 5 (1equivalent). The reaction R-2 is a Wittig reaction.

In the reaction R-2, at least 1 mole and no greater than 10 moles of thecompound 4 is preferably added relative to 1 mole of the compound 3. Ifthe number of moles of the compound 4 is too small relative to thenumber of moles of the compound 3, there may be a reduction in the yieldof the compound 5. If the number of moles of the compound 4 is too largerelative to the number of moles of the compound 3, purification of thecompound 5 may be difficult due to the compound 4 remaining unreacted.

The reaction R-2 may be carried out in the presence of a base. Examplesof bases that can be used include sodium alkoxides (specifically, sodiummethoxide and sodium ethoxide), metal hydrides (specifically, sodiumhydride and potassium hydride), and metal salts (specifically, n-butyllithium). Any one of the bases listed above may be used independently,or any two or more of the bases listed above may be used in combination.The additive amount of the base is preferably at least 1 mole and nogreater than 2 moles relative to 1 mole of the compound 4. If theadditive amount of the base is too small, there may be a reduction inreactivity. On the other hand, if the additive amount of the base is toolarge, the reaction may be difficult to control.

The reaction R-2 may be carried out in a solvent. Examples of solventsthat can be used include ethers (specifically, tetrahydrofuran, diethylether, and dioxane), halogenated hydrocarbons (specifically, methylenechloride, chloroform, and dichloroethane), and aromatic hydrocarbons(specifically, benzene and toluene).

The reaction temperature of the reaction R-2 is preferably at least 0°C. and no greater than 50° C., and the reaction time thereof ispreferably at least 2 hours and no greater than 24 hours.

(Reaction R-3)

In the reaction R-3, the compound 6 (1 equivalent) is caused to reactwith triethyl phosphite (1 equivalent) to give the compound 7 (1equivalent).

In the reaction R-3, at least 1 mole and no greater than 2.5 moles oftriethyl phosphite is preferably added relative to 1 mole of thecompound 6. If the number of moles of triethyl phosphite is too smallrelative to the number of moles of the compound 6, there may be areduction in the yield of the compound 7. On the other hand, if thenumber of moles of the triethyl phosphite is too large relative to thenumber of moles of the compound 6, purification of the compound 7 afterthe reaction may be difficult due to triethyl phosphite remainingunreacted.

The reaction temperature of the reaction R-3 is preferably at least 160°C. and no greater than 200° C., and the reaction time thereof ispreferably at least 2 hours and no greater than10 hours.

(Reaction R-4)

In the reaction R-4, the compound 7 (1 equivalent) is caused to reactwith the compound 5 (1 equivalent) to give the compound 8 (1equivalent). The reaction R-4 is a Wittig reaction.

In the reaction R-4, at least 1 mole and no greater than 2.5 moles ofthe compound 5 is preferably added relative to 1 mole of the compound 7.If the number of moles of the compound 5 is too small relative to thenumber of moles of the compound 7, there may be a reduction in the yieldof the compound 8. If the number of moles of the compound 5 is too largerelative to the number of moles of the compound 7, purification of thecompound 8 may be difficult due to the compound 5 remaining unreacted.

The reaction R-4 may be carried out in the presence of a base. Examplesof bases that can be used are the same as for the reaction R-2. Any oneof the bases listed above may be used independently, or any two or moreof the bases listed above may be used in combination. The additiveamount of the base is preferably at least 1 mole and no greater than 2moles relative to 1 mole of the compound 5. If the additive amount ofthe base is too small, there may be a reduction in reactivity. On theother hand, if the additive amount of the base is too large, thereaction may be difficult to control.

The reaction R-4 may be carried out in a solvent. Examples of solventsthat can be used are the same as for the reaction R-2. The reactiontemperature of the reaction R-4 is preferably at least 0° C. and nogreater than 50° C., and the reaction time thereof is preferably atleast 2 hours and no greater than 24 hours.

(Reaction R-5)

In the reaction R-5, the compound 9 (2 equivalents) is caused to reactwith the compound 10 (1 equivalent) to give the compound 11 (1equivalent). The reaction R-5 is a coupling reaction.

In the reaction R-5, at least 2 moles and no greater than 10 moles ofthe compound 9 is preferably added relative to 1 mole of the compound10. If the number of moles of the compound 9 is too small relative tothe number of moles of the compound 10, there may be a reduction in theyield of the compound 11. If the number of moles of the compound 9 istoo large relative to the number of moles of the compound 10,purification of the compound 11 after the reaction may be difficult dueto the compound 9 remaining unreacted.

The reaction temperature of the reaction R-5 is preferably at least 80°C. and no greater than 140° C., and the reaction time thereof ispreferably at least 2 hours and no greater than10 hours.

In the reaction R-5, a palladium compound is preferably used as acatalyst. Use of the palladium compound tends to enable a reduction inthe activation energy of the reaction R-5. As a result, the yield of thecompound 11 is expected to be increased. Examples of palladium compoundsthat can be used include tetravalent palladium compounds, divalentpalladium compounds, and other palladium compounds. Specific examples oftetravalent palladium compounds include hexachloro palladium(IV) sodiumtetrahydrate and hexachloro palladium(IV) potassium tetrahydrate.Specific examples of divalent palladium compounds include palladium(II)chloride, palladium(II) bromide, palladium(II) acetate, palladium(II)acetylacetate, dichlorobis(benzonitrile)palladium(II),dichlorobis(triphenylphosphine)palladium(II), dichlorotetraminepalladium(II), and dichloro(cycloocta-1,5-diene)palladium(II). Examplesof other palladium compounds includetris(dibenzylideneacetone)dipalladium(0),tris(dibenzylideneacetone)dipalladium(0) chloroform complex, andtetrakis(triphenylphosphine)palladium(0). Any one of the palladiumcompounds listed above may be used independently, or any two or more ofthe palladium compounds listed above may be used in combination. Theadditive amount of the palladium compound is preferably at least 0.0005moles and no greater than 20 moles relative to 1 mole of the compound10, and more preferably at least 0.001 moles and no greater than 1 mole.

The palladium compound may have a structure including a ligand. As aresult, reactivity of the reaction R-5 can be readily improved. Examplesof ligands that can be used include tricyclohexylphosphine,triphenylphosphine, methyldiphenylphosphine, trifurylphosphine,tri(o-tolyl)phosphine, dicyclohexylphenylphosphine,tri(t-butyl)phosphine, 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl, and2,2′-bis[(diphenylphosphino)diphenyl] ether. Any one of the ligandslisted above may be used independently, or any two or more of theligands listed above may be used in combination. The additive amount ofthe ligand is preferably at least 0.0005 moles and no greater than 20moles relative to 1 mole of the compound 10, and more preferably atleast 0.001 moles and no greater than 1 mole.

The reaction R-5 is preferably carried out in the presence of a base.Through the presence of the base, hydrogen halide (for example, hydrogenchloride) produced in the reaction system can be quickly neutralized andcatalytic activity can be improved. As a result, the yield of thecompound 11 is expected to be improved. The base may be an inorganicbase or an organic base. Preferably, organic bases for example includealkali metal alkoxides (specifically, sodium methoxide, sodium ethoxide,potassium methoxide, potassium ethoxide, lithium tert-butoxide, sodiumtert-butoxide, and potassium tert-butoxide), with sodium tert-butoxidebeing more preferable. Examples of inorganic bases that can be usedinclude tripotassium phosphate and cesium fluoride. In a situation inwhich at least 0.0005 moles and no greater than 20 moles of thepalladium compound is added relative to 1 mole of the compound 10, theadditive amount of the base is preferably at least 1 mole and no greaterthan 50 moles, and more preferably at least 1 mole and no greater than30 moles.

The reaction R-5 may be carried out in a solvent. Examples of solventsthat can be used include xylene (specifically, o-xylene), toluene,tetrahydrofuran, and dimethyl formamide.

(Reaction R-6)

In the reaction R-6, the compound 11(1 equivalent) is caused to reactwith the compound 8 (2 equivalents) to give the benzidine derivative 1(1 equivalent). The reaction R-6 is a coupling reaction.

In the reaction R-6, at least 2 moles and no greater than 10 moles ofthe compound 8 is preferably added relative to 1 mole of the compound11. If the number of moles of the compound 8 is too small relative tothe number of moles of the compound 11, there may be a reduction in theyield of the benzidine derivative 1. On the other hand, if the number ofmoles of the compound 8 is too large relative to the number of moles ofthe compound 11, purification of the benzidine derivative 1 after thereaction may be difficult due to the compound 8 remaining unreacted.

The reaction temperature of the reaction R-6 is preferably at least 80°C. and no greater than140° C., and the reaction time thereof ispreferably at least 2 hours and no greater than 10 hours.

In the reaction R-6, a palladium compound is preferably used as acatalyst. Use of the palladium compound tends to enable a reduction inthe activation energy of the reaction R-6. As a result, the yield of thebenzidine derivative 1 is expected to be increased. Examples ofpalladium compounds that can be used are the same as for the reactionR-5. Any one of the palladium compounds listed above may be usedindependently, or any two or more of the palladium compounds listedabove may be used in combination. The additive amount of the palladiumcompound is preferably at least 0.0005 moles and no greater than 20moles relative to 1 mole of the compound 11, and more preferably atleast 0.001 moles and no greater than 1 mole.

The palladium compound may have a structure including a ligand. As aresult, reactivity of the reaction R-6 is expected to be improved.Examples of ligands that can be used are the same as for the reactionR-5. Any one of the ligands listed above may be used independently, orany two or more of the ligands listed above may be used in combination.The additive amount of the ligand is preferably at least 0.0005 molesand no greater than 20 moles relative to 1 mole of the compound 11, andmore preferably at least 0.001 moles and no greater than 1 mole.

The reaction R-6 is preferably carried out in the presence of a base.Through the presence of the base, hydrogen halide (for example, hydrogenchloride) produced in the reaction system can be quickly neutralized andcatalytic activity can be improved. As a result, the yield of thebenzidine derivative 1 is expected to be increased. Examples of basesthat can be used are the same as for the reaction R-5. In a situation inwhich at least 0.0005 moles and no greater than 20 moles of thepalladium compound is added relative to 1 mole of the compound 11, theadditive amount of the base is preferably at least 1 mole and no greaterthan 10 moles, and more preferably at least 1 mole and no greater than 5moles.

The reaction R-6 may be carried out in a solvent. Examples of solventsthat can be used are the same as for the reaction R-5.

Through the above, the benzidine derivative and the method for producingthe benzidine derivative according to the present embodiment have beendescribed. Through the benzidine derivative according to the presentembodiment being contained in a photosensitive layer of a photosensitivemember, crystallization in the photosensitive layer can be inhibited andelectrical properties of the photosensitive member can be improved. Themethod for producing the triphenylamine derivative according to thepresent embodiment enables production of the benzidine derivative thatinhibits crystallization in the photosensitive layer and improveselectrical properties of the photosensitive member.

[Photosensitive Member]

The following describes a photosensitive member containing the benzidinederivative according to the present embodiment. The photosensitivemember may be a multi-layer photosensitive member or a single-layerphotosensitive member. The photosensitive member includes aphotosensitive layer. The photosensitive layer contains at least acharge generating material and the benzidine derivative 1 as a holetransport material.

<1. Multi-Layer Photosensitive Member>

The following describes a configuration in which a photosensitive member100 is a multi-layer photosensitive member with reference to FIGS. 3A to3C. FIGS. 3A to 3C are schematic cross sectional views each illustratinga multi-layer photosensitive member, which is an example of thephotosensitive member 100.

As illustrated in FIG. 3A, the multi-layer photosensitive member servingas the photosensitive member 100 includes a conductive substrate 20 anda photosensitive layer 30. The multi-layer photosensitive memberincludes, as the photosensitive layer 30, a charge generating layer 30 aand a charge transport layer 30b. The conductive substrate 20 will bedescribed later.

As illustrated in FIG. 3B, the charge transport layer 30 b may bedisposed on the conductive substrate 20 and the charge generating layer30 a may be disposed on the charge transport layer 30 b in themulti-layer photosensitive member serving as the photosensitive member100. However, the charge transport layer 30 b typically has a greaterfilm thickness than the charge generating layer 30 a, and therefore thecharge transport layer 30 b is more resistant to damage than the chargegenerating layer 30 a. In order to improve abrasion resistance of themulti-layer photosensitive member, therefore, the charge transport layer30 b is preferably disposed on the charge generating layer 30 a asillustrated in FIG. 3A.

As illustrated in FIG. 3C, the multi-layer photosensitive member servingas the photosensitive member 100 may include the conductive substrate20, the photosensitive layer 30, and an intermediate layer (undercoatlayer) 40. The intermediate layer 40 is disposed between the conductivesubstrate 20 and the photosensitive layer 30. Furthermore, a protectivelayer (not illustrated) may be disposed on the photosensitive layer 30.

No particular limitations are placed on thicknesses of the chargegenerating layer 30 a and the charge transport layer 30 b so long as thethicknesses thereof are sufficient to enable the layers to implementtheir respective functions. The charge generating layer 30 a preferablyhas a thickness of at least 0.01 82 m and no greater than 5 μm, and morepreferably at least 0.1 μm and no greater than 3 μm. The chargetransport layer 30 b preferably has a thickness of at least 2 μm and nogreater than 100 μm, and more preferably at least 5 μm and no greaterthan 50 μm.

The charge generating layer 30 a in the photosensitive layer 30 containsa charge generating material. The charge generating layer 30 a containsa charge generating layer binder resin (hereinafter, may be referred toas a base resin) and various additives as necessary. The chargegenerating material, the base resin, and the additives will be describedlater.

The charge transport layer 30 b in the photosensitive layer 30 containsa hole transport material. The charge transport layer 30 b may contain abinder resin, an electron acceptor compound, and various additives asnecessary. The hole transport material, the binder resin, the electronacceptor compound, and the additives will be described later. Throughthe above, a configuration in which the photosensitive member 100 is amulti-layer photosensitive member has been described with reference toFIGS. 3A to 3C.

<2. Single-Layer Photosensitive Member>

The following describes a configuration in which the photosensitivemember 100 is a single-layer photosensitive member with reference toFIGS. 4A to 4C. FIGS. 4A to 4C are schematic cross sectional views eachillustrating a single-layer photosensitive member, which is anotherexample of the photosensitive member 100.

As illustrated in FIG. 4A, the single-layer photosensitive memberserving as the photosensitive member 100 includes the conductivesubstrate 20 and the photosensitive layer 30. The single-layerphotosensitive member serving as the photosensitive member 100 includesa single-layer type photosensitive layer 30 c as the photosensitivelayer 30. The conductive substrate 20 will be described later.

As illustrated in FIG. 4B, the single-layer photosensitive memberserving as the photosensitive member 100 may include the conductivesubstrate 20, the single-layer type photosensitive layer 30 c, and theintermediate layer (undercoat layer) 40. The intermediate layer 40 isdisposed between the conductive substrate 20 and the single-layer typephotosensitive layer 30 c. Furthermore, as illustrated in FIG. 4C, aprotective layer 50 may be disposed on the single-layer typephotosensitive layer 30 c.

No particular limitations are placed on thickness of the single-layertype photosensitive layer 30 c, so long as the thickness thereof issufficient to enable the single-layer type photosensitive layer 30 c tofunction as a single-layer type photosensitive layer. The single-layertype photosensitive layer 30 c preferably has a thickness of at least 5μm and no greater than 100 μm, and more preferably at least 10 μm and nogreater than 50 μm.

The single-layer type photosensitive layer 30 c serving as thephotosensitive layer 30 contains a charge generating material and a holetransport material. The single-layer type photosensitive layer 30 c maycontain an electron transport material, a binder resin, and variousadditives as necessary. The hole transport material, the chargegenerating material, the electron transport material, the binder resin,and the additives will be described later. Through the above, aconfiguration in which the photosensitive member 100 is a single-layerphotosensitive member has been described with reference to FIGS. 4A to4C.

The following describes elements of configuration that are common to thephotosensitive member for both the multi-layer photosensitive member andthe single-layer photosensitive member.

<3. Conductive Substrate>

No particular limitations are placed on the conductive substrate otherthan being a conductive substrate that can be used in photosensitivemembers. At least a surface portion of the conductive substrate isformed from a conductive material. An example of the conductivesubstrate is a conductive substrate formed from a conductive material.Another example of the conductive substrate is a conductive substrateformed through coating with a conductive material. Examples ofconductive materials that can be used include aluminum, iron, copper,tin, platinum, silver, vanadium, molybdenum, chromium, cadmium,titanium, nickel, palladium, indium, stainless steel, and brass. Any oneof the conductive materials listed above may be used independently, orany two or more of the conductive materials listed above may be used incombination (for example, as an alloy). Of the conductive materialslisted above, aluminum or aluminum alloy is preferable in terms of goodcharge mobility from the photosensitive layer to the conductivesubstrate.

The shape of the conductive substrate is selected as appropriate inaccordance with the structure of an image forming apparatus in which theconductive substrate is to be used. The conductive substrate may forexample be sheet-shaped or drum-shaped. Furthermore, the thickness ofthe conductive substrate is selected as appropriate in accordance withthe shape of the conductive substrate.

<4. Hole Transport Material>

The photosensitive layer contains the benzidine derivative 1 as a holetransport material. In a configuration in which the photosensitivemember is a multi-layer photosensitive member, the charge transportlayer contains the benzidine derivative 1 as the hole transportmaterial. In a configuration in which the photosensitive member is asingle-layer photosensitive member, the single-layer type photosensitivelayer contains the benzidine derivative 1 as the hole transportmaterial. As a result of the photosensitive layer containing thebenzidine derivative 1, as already described above, crystallization inthe photosensitive layer can be inhibited and electrical properties ofthe photosensitive member can be improved.

<5. Charge Generating Material>

In a configuration in which the photosensitive member is a multi-layerphotosensitive member, the charge generating layer contains a chargegenerating material. In a configuration in which the photosensitivemember is a single-layer photosensitive member, the single-layer typephotosensitive layer contains a charge generating material.

No particular limitations are placed on the charge generating materialother than being a charge generating material that can be used inphotosensitive members. Examples of charge generating materials that canbe used include phthalocyanine-based pigments, perylene-based pigments,bisazo pigments, trisazo pigments, dithioketopyrrolopyrrole pigments,metal-free naphthalocyanine pigments, metal naphthalocyanine pigments,squaraine pigments, indigo pigments, azulenium pigments, cyaninepigments, powders of inorganic photoconductive materials (for example,selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, oramorphous silicon), pyrylium pigments, anthanthrone-based pigments,triphenylmethane-based pigments, threne-based pigments, toluidine-basedpigments, pyrazoline-based pigments, and quinacridone-based pigments.

Examples of phthalocyanine-based pigments that can be used include ametal-free phthalocyanine represented by chemical formula (CG-1) andmetal phthalocyanine. Examples of the metal phthalocyanine includetitanyl phthalocyanine represented by chemical formula (CG-2),hydroxygallium phthalocyanine, and chlorogallium phthalocyanine. Thephthalocyanine-based pigment may be crystalline or non-crystalline. Noparticular limitations are placed on the crystal structure (for example,α-form, β-form, Y-form, V-form, or II-form) of the phthalocyanine-basedpigment, and phthalocyanine-based pigments having various differentcrystal structures may be used.

Examples of crystalline metal-free phthalocyanine that can be usedinclude metal-free phthalocyanine having an X-form crystal structure(hereinafter, may be referred to as X-form metal-free phthalocyanine).Examples of crystalline titanyl phthalocyanine include titanylphthalocyanine having an α-form, β-form, or Y-form crystal structure(hereinafter, may be referred to as α-form, β-form, or Y-form titanylphthalocyanine). Examples of crystalline hydroxygallium phthalocyanineinclude hydroxygallium phthalocyanine having a V-form crystal structure.Examples of crystalline chlorogallium phthalocyanine includechlorogallium phthalocyanine having a II-form crystal structure. X-formmetal-free phthalocyanine and Y-form titanyl phthalocyanine arepreferable as each having a high quantum yield for a wavelength regionof 700 nm or greater. In order to particularly improve electricalproperties in the case of the photosensitive layer containing thebenzidine derivative 1 as the hole transport material, Y-form titanylphthalocyanine is more preferable.

Y-form titanyl phthalocyanine for example exhibits a major peak at aBragg angle (2θ±0.2°) of 27.2° with respect to CuKα characteristic X-raydiffraction spectrum. The term major peak refers to a most intense orsecond most intense peak within a range of Bragg angles (2θ±0.2°) from3° to 40° in a CuKα characteristic X-ray diffraction spectrum.

(Method for Measuring Cukα Characteristic X-Ray Diffraction Spectrum)

An example of methods for measuring a CuKα characteristic X-raydiffraction spectrum will be described. A sample (titanylphthalocyanine) is loaded into a sample holder of an X-ray diffractionspectrometer (for example, “RINT (registered Japanese trademark) 1100”,product of Rigaku Corporation) and an X-ray diffraction spectrum ismeasured using a Cu X-ray tube, a tube voltage of 40 kV, a tube currentof 30 mA, and X-rays characteristic of CuKα having a wavelength of 1.542Å. The measurement range (2θ) is for example from 3° to 40° (startangle: 3°, stop angle: 40°) and the scanning speed is for example10°/minute.

A single charge generating material having an absorption wavelength in adesired region or a combination of two or more charge generatingmaterials may be used. Also, for example in a digital optical systemimage forming apparatus (for example, a laser beam printer or facsimilemachine in which a light source such as a semiconductor laser is used),a photosensitive member that is sensitive to a range of wavelengths thatare greater than or equal to 700 nm is preferably used. Accordingly, forexample, a phthalocyanine-based pigment is preferable, metal-freephthalocyanine or titanyl phthalocyanine is more preferable, and X-formmetal-free phthalocyanine or Y-form titanyl phthalocyanine isparticularly preferable. One charge generating material may be usedindependently, or two or more charge generating materials may be used incombination.

For a photosensitive member applied to an image forming apparatus thatuses a short-wavelength laser light source (for example, a laser lightsource having an approximate wavelength of at least 350 nm and nogreater than 550 nm), an anthanthrone-based pigment is preferably usedas the charge generating material.

In a configuration in which the photosensitive member is a multi-layerphotosensitive member, the amount of the charge generating material ispreferably at least 5 parts by mass and no greater than 1,000 parts bymass relative to 100 parts by mass of the base resin contained in thecharge generating layer, and more preferably at least 30 parts by massand no greater than 500 parts by mass.

In a configuration in which the photosensitive member is a single-layerphotosensitive member, the amount of the charge generating material ispreferably at least 0.1 parts by mass and no greater than 50 parts bymass relative to 100 parts by mass of the binder resin contained in thesingle-layer type photosensitive layer, and more preferably at least 0.5parts by mass and no greater than 30 parts by mass.

<6. Electron Transport Material and Electron Acceptor Compound>

In a configuration in which the photosensitive member is a multi-layerphotosensitive member, the charge transport layer may contain anelectron acceptor compound as necessary. As a result, the hole transportby the hole transport material tends to be improved. On the other hand,in a situation in which the photosensitive member is a single-layerphotosensitive member, the single-layer type photosensitive layer maycontain an electron transport material as necessary. Through inclusionof the electron transport material, the single-layer type photosensitivelayer can transport electrons and the single-layer type photosensitivelayer can be easily provided with bipolar properties.

Examples of electron transport materials or electron acceptor compoundsthat can be used include quinone-based compounds, diimide-basedcompounds, hydrazone-based compounds, malononitrile-based compounds,thiopyran-based compounds, trinitrothioxanthone-based compounds,3,4,5,7-tetranitro-9-fluorenone-based compounds, dinitroanthracene-basedcompounds, dinitroacridine-based compounds, tetracyanoethylene,2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroacridine, succinicanhydride, maleic anhydride, and dibromomaleic anhydride. Examples ofquinone-based compounds that can be used include diphenoquinone-basedcompounds, azoquinone-based compounds, anthraquinone-based compounds,naphthoquinone-based compounds, nitroanthraquinone-based compounds, anddinitroanthraquinone-based compounds. One electron transport materialmay be used independently, or two or more electron transport materialsmay be used in combination. Likewise, one electron acceptor compound maybe used independently, or two or more electron acceptor compounds may beused in combination.

Examples of the electron transport material or the electron acceptorinclude compounds represented by general formulae (12) to (14).

In the general formulae (12) to (14), R₁₁ to R₁₉ each represent,independently of one another, a hydrogen atom, a cyano group, anoptionally substituted alkyl group, an optionally substituted alkenylgroup, an optionally substituted alkoxy group, an optionally substitutedalkoxycarbonyl group, an optionally substituted aryl group, or anoptionally substituted heterocyclic group.

The alkyl group represented by R₁₁ to R₁₉ in the general formulae (12)to (14) is for example an alkyl group having a carbon number of at least1 and no greater than 6. The alkyl group having a carbon number of atleast 1 and no greater than 6 is preferably an alkyl group having acarbon number of at least 1 and no greater than 5, and more preferably amethyl group, a 1,1-dimethylpropyl group, or a tert-butyl group. Thealkyl group is optionally substituted. The alkyl group may for examplehave, as a substituent, a halogen atom, a hydroxyl group, an alkoxygroup having a carbon number of at least 1 and no greater than 6, anaryl group having a carbon number of at least 6 and no greater than 14and optionally bearing further substituents, or a cyano group. Althoughno particular limitations are placed on the number of substituents, thealkyl group preferably has no greater than three substituents. Examplesof substituents that are further borne by the aryl group that is asubstituent of alkyl and that has a carbon number of at least 6 and nogreater than 14 include a halogen atom, a hydroxyl group, an alkyl grouphaving a carbon number of at least 1 and no greater than 6, an alkoxygroup having a carbon number of at least 1 and no greater than 6, anitro group, a cyano group, an alkanoyl group having a carbon number ofat least 2 and no greater than 7 (a group formed through bonding of acarbonyl group with an alkyl group having a carbon number of at least 1and no greater than 6), a benzoyl group, a phenoxy group, analkoxycarbonyl group having a carbon number of at least 2 and no greaterthan 7 (a group formed through bonding of a carbonyl group with analkoxy group having a carbon number of at least 1 and no greater than6), and a phenoxycarbonyl group.

The alkenyl group represented by R₁₁ to R₁₉ in the general formulae (12)to (14) is for example an unsubstituted straight chain or branched chainalkenyl group having a carbon number of at least 2 and no greater than6. The alkenyl group having a carbon number of at least 2 and no greaterthan 6 for example has at least one and no greater than three doublebonds. The alkenyl group having a carbon number of at least 2 and nogreater than 6 is for example a vinyl group, a propenyl group, a butenylgroup, a pentenyl group, a pentadienyl group, a hexenyl group, or ahexadienyl group. The alkenyl group is optionally substituted. Thealkenyl group may for example have, as a substituent, a halogen atom, ahydroxyl group, an alkoxy group having a carbon number of at least 1 andno greater than 6, an aryl group having a carbon number of at least 6and no greater than 14, or a cyano group. Although no particularlimitations are placed on the number of substituents, the alkenyl grouppreferably has no greater than three substituents.

The alkoxy group represented by R₁₁ to R₁₉ in the general formulae (12)to (14) is for example an alkoxy group having a carbon number of atleast 1 and no greater than 6. The alkoxy group having a carbon numberof at least 1 and no greater than 6 is preferably an alkoxy group havinga carbon number of at least 1 and no greater than 3, and more preferablya methoxy group. The alkoxy group is optionally substituted. The alkoxygroup may for example have, as a substituent, a halogen atom, a hydroxylgroup, an alkoxy group having a carbon number of at least 1 and nogreater than 6, an aryl group having a carbon number of at least 6 andno greater than 14, or a cyano group. Preferably, the substituent is aphenyl group. Although no particular limitations are placed on thenumber of substituents, the alkoxy group preferably has no greater thanthree substituents, and more preferably has one substituent.

The alkoxycarbonyl group represented by R₁₁ to R₁₉ in the generalformulae (12) to (14) is for example an alkoxycarbonyl group having acarbon number of at least 2 and no greater than 7. An alkoxycarbonylgroup having a carbon number of at least 2 and no greater than 7 as usedherein refers to a group formed through bonding of a carbonyl group withan unsubstituted straight chain or branched chain alkoxy group having acarbon number of at least 1 and no greater than 6. The alkoxycarbonylgroup is optionally substituted. The alkoxycarbonyl group may forexample have, as a substituent, a halogen atom, a hydroxyl group, analkoxy group having a carbon number of at least 1 and no greater than 6,an aryl group having a carbon number of at least 6 and no greater than14, or a cyano group. Although no particular limitations are placed onthe number of substituents, the alkoxycarbonyl group preferably has nogreater than three substituents.

The aryl group represented by R₁₁ to R₁₉ in the general formulae (12) to(14) is for example an aryl group having a carbon number of at least 6and no greater than 14. The aryl group having a carbon number of atleast 6 and no greater than 14 is preferably a phenyl group. The arylgroup is optionally substituted. The aryl group may for example have, asa substituent, a halogen atom, a hydroxyl group, an alkyl group having acarbon number of at least 1 and no greater than 6, an alkoxy grouphaving a carbon number of at least 1 and no greater than 6, a nitrogroup, a cyano group, an alkanoyl group having a carbon number of atleast 2 and no greater than 7 (a group formed through bonding of acarbonyl group with an alkyl group having a carbon number of at least 1and no greater than 6), a benzoyl group, a phenoxy group, analkoxycarbonyl group having a carbon number of at least 2 and no greaterthan 7 (a group formed through bonding of a carbonyl group with analkoxy group having a carbon number of at least 1 and no greater than6), a phenoxycarbonyl group, an aryl group having a carbon number of atleast 6 and no greater than 14, or a biphenyl group. Although noparticular limitations are placed on the number of substituents, thearyl group preferably has no greater than three substituents.

The heterocyclic group represented by R₁₁ to R₁₉ in the general formulae(12) to (14) is for example a heterocyclic group formed by a five- orsix-membered monocyclic ring including at least one hetero atom selectedfrom the group consisting of N, S, and O; a heterocyclic group resultingfrom condensation of a plurality of such monocyclic rings; or aheterocyclic group resulting from condensation of such a monocyclic ringwith a five- or six-membered hydrocarbon ring. In a configuration inwhich the heterocyclic group is a fused ring structure, the fused ringstructure preferably includes no greater than three rings. Theheterocyclic group may for example have, as a substituent, a halogenatom, a hydroxyl group, an alkyl group having a carbon number of atleast 1 and no greater than 6, an alkoxy group having a carbon number ofat least 1 and no greater than 6, a nitro group, a cyano group, analkanoyl group having a carbon number of at least 2 and no greater than7 (a group formed through bonding of a carbonyl group with an alkylgroup having a carbon number of at least 1 and no greater than 6), abenzoyl group, a phenoxy group, an alkoxycarbonyl group having a carbonnumber of at least 2 and no greater than 7 (a group formed throughbonding of a carbonyl group with an alkoxy group having a carbon numberof at least 1 and no greater than 6), and a phenoxycarbonyl group.Although no particular limitations are placed on the number ofsubstituents, the heterocyclic group preferably has no greater thanthree substituents.

In order to improve electrical properties of the photosensitive memberin which the photosensitive layer is a single-layer type photosensitivelayer and that contains the benzidine derivative 1 as a hole transportmaterial, the compound represented by the general formula (12) ispreferably used.

Specific examples of the compounds represented by the general formulae(12) to (14) include compounds represented by chemical formulae (ET-1)to (ET-3). Hereinafter, the compounds represented by the chemicalformulae (ET-1) to (ET-3) may be referred to as compounds ET-1 to ET-3.

In a configuration in which the photosensitive member is a multi-layerphotosensitive member, the amount of the electron acceptor compound ispreferably at least 0.1 parts by mass and no greater than 20 parts bymass relative to 100 parts by mass of the binder resin contained in thecharge transport layer, and more preferably at least 0.5 parts by massand no greater than 10 parts by mass.

In a configuration in which the photosensitive member is a single-layerphotosensitive member, the amount of the electron transport material ispreferably at least 5 parts by mass and no greater than 100 parts bymass relative to 100 parts by mass of the binder resin contained in thesingle-layer type photosensitive layer, and more preferably at least 10parts by mass and no greater than 80 parts by mass.

<7. Binder Resin>

In a configuration in which the photosensitive member is a multi-layerphotosensitive member, the charge transport layer contains a binderresin. In a configuration in which the photosensitive member is asingle-layer photosensitive member, the single-layer type photosensitivelayer contains a binder resin.

Examples of binder resins that can be used include thermoplastic resins,thermosetting resins, and photocurable resins. Examples of thermoplasticresins that can be used include polycarbonate resins, polyarylateresins, styrene-butadiene copolymers, styrene-acrylonitrile copolymers,styrene-maleic acid copolymers, acrylic acid copolymers, styrene-acrylicacid copolymers, polyethylene resins, ethylene-vinyl acetate copolymers,chlorinated polyethylene resins, polyvinyl chloride resins,polypropylene resins, ionomer resins, vinyl chloride-vinyl acetatecopolymers, alkyd resins, polyamide resins, urethane resins, polysulfoneresins, diallyl phthalate resins, ketone resins, polyvinyl butyralresins, polyester resins, and polyether resins. Examples ofthermosetting resins that can be used include silicone resins, epoxyresins, phenolic resins, urea resins, and melamine resins. Examples ofphotocurable resins that can be used include epoxy acrylate (acrylicacid adducts of epoxy compounds) and urethane acrylate (acrylic acidadducts of urethane compounds). Any one of the binder resins listedabove may be used independently, or any two or more of the binder resinslisted above may be used in combination.

Of the binder resins listed above, polycarbonate resins are preferablefor obtaining a single-layer type photosensitive layer and a chargetransport layer having excellent balance in terms of processability,mechanical properties, optical properties, and abrasion resistance.Examples of polycarbonate resins that can be used include bisphenol Zpolycarbonate resin, bisphenol ZC polycarbonate resin, bisphenol Cpolycarbonate resin, and bisphenol A polycarbonate resin.

The binder resin preferably has a viscosity average molecular weight ofat least 40,000, and more preferably at least 40,000 and no greater than52,500. As a result of the binder resin having a viscosity averagemolecular weight of at least 40,000, abrasion resistance of thephotosensitive member can be readily improved. As a result of the binderresin having a viscosity average molecular weight of no greater than52,500, the binder resin has a high tendency to dissolve in a solventand viscosity of an application liquid for charge transport layerformation or an application liquid for single-layer type photosensitivelayer formation has a low tendency to be too high during photosensitivelayer formation. Consequently, the charge transport layer or thesingle-layer type photosensitive layer can be readily formed.

<8. Base Resin>

In a configuration in which the photosensitive member is a multi-layerphotosensitive member, the charge generating layer contains a baseresin. No particular limitations are placed on the base resin so long asthe base resin can be used in photosensitive members. Examples of baseresins that can be used include thermoplastic resins, thermosettingresins, and photocurable resins. Examples of thermoplastic resins thatcan be used include styrene-butadiene copolymers, styrene-acrylonitrilecopolymers, styrene-maleic acid copolymers, styrene-acrylic acidcopolymers, acrylic copolymers, polyethylene resins, ethylene-vinylacetate copolymers, chlorinated polyethylene resins, polyvinyl chlorideresins, polypropylene resins, ionomers, vinyl chloride-vinyl acetatecopolymers, alkyd resins, polyamide resins, urethane resins,polycarbonate resins, polyarylate resins, polysulfone resins, diallylphthalate resins, ketone resins, polyvinyl butyral resins, polyetherresins, and polyester resins. Examples of thermosetting resins that canbe used include silicone resins, epoxy resins, phenolic resins, urearesins, melamine resins, and other crosslinkable thermosetting resins.Examples of photocurable resins that can be used include epoxy acrylate(acrylic acid adducts of epoxy compounds) and urethane acrylate (acrylicacid adducts of urethane compounds). Any one of the base resins listedabove may be used independently, or any two or more of the base resinslisted above may be used in combination.

Preferably, the base resin contained in the charge generating layer isdifferent from the binder resin contained in the charge transport layerfor the following reason. In production of a multi-layer photosensitivemember, for example, a charge generating layer is formed on a conductivesubstrate, and a charge transport layer is formed on the chargegenerating layer. In the formation of the charge transport layer, anapplication liquid for charge transport layer formation is applied ontothe charge generating layer. Therefore, the charge generating layer ispreferably insoluble in a solvent of the application liquid for chargetransport layer formation.

<9. Additive>

The photosensitive layer of the photosensitive member (the chargegenerating layer, the charge transport layer, or the single-layer typephotosensitive layer) may contain various additives as necessary.Examples of additives that can be used include antidegradants (specificexamples include antioxidants, radical scavengers, singlet quenchers,and ultraviolet absorbing agents), softeners, surface modifiers,extending agents, thickeners, dispersion stabilizers, waxes, acceptors,donors, surfactants, plasticizers, sensitizers, and leveling agents.Examples of antioxidants include hindered phenols (specific examplesinclude di(tert-butyl)p-cresol), hindered amines, paraphenylenediamine,arylalkanes, hydroquinone, spirochromanes, spiroindanones, derivativesof any of the above compounds, organosulfur compounds, andorganophosphorus compounds.

<10. Intermediate Layer>

The intermediate layer (undercoat layer) for example contains inorganicparticles and a resin for intermediate layer use (intermediate layerresin). Provision of the intermediate layer may facilitate flow ofcurrent generated when the photosensitive member is exposed to light andinhibit increasing resistance, while also maintaining insulation to asufficient degree so as to inhibit leakage current from occurring.

Examples of inorganic particles that can be used include particles ofmetals (for example, aluminum, iron, and copper), particles of metaloxides (for example, titanium oxide, alumina, zirconium oxide, tinoxide, and zinc oxide), and particles of non-metal oxides (for example,silica). Any one type of the inorganic particles listed above may beused independently, or any two or more types of the inorganic particleslisted above may be used in combination.

No particular limitations are placed on the intermediate layer resin solong as the resin can be used for forming the intermediate layer. Theintermediate layer may contain various additives. The additives are thesame as defined for the additives for the photosensitive layer.

<11. Method for Producing Photosensitive Member>

In a configuration in which the photosensitive member is a multi-layerphotosensitive member, the multi-layer photosensitive member is forexample produced as described below. First, an application liquid forcharge generating layer formation and an application liquid for chargetransport layer formation are prepared. The application liquid forcharge generating layer formation is applied onto the conductivesubstrate and dried to form the charge generating layer. Next, theapplication liquid for charge transport layer formation is applied ontothe charge generating layer and dried to form the charge transportlayer. Through the above, the multi-layer photosensitive member isproduced.

The application liquid for charge generating layer formation is preparedby dissolving or dispersing a charge generating material and optionalcomponents (for example, a base resin and various additives), dependingon necessity thereof, in a solvent. The application liquid for chargetransport layer formation is prepared by dissolving or dispersing a holetransport material and optional components (for example, a binder resin,an electron acceptor compound, and various additives), depending onnecessity thereof, in a solvent.

In a configuration in which the photosensitive member is a single-layerphotosensitive member, the single-layer photosensitive member is forexample produced as described below. The single-layer photosensitivemember is produced by applying an application liquid for single-layertype photosensitive layer formation onto the conductive substrate anddrying the application liquid for single-layer type photosensitive layerformation. The application liquid for single-layer type photosensitivelayer formation is prepared by dissolving or dispersing a chargegenerating material, a hole transport material, and optional components(for example, an electron transport material, a binder resin, andvarious additives), depending on necessity thereof, in a solvent.

No particular limitations are placed on the solvents contained in theapplication liquids (the application liquid for charge generating layerformation, the application liquid for charge transport layer formation,or the application liquid for single-layer type photosensitive layerformation) other than that the components of each of the applicationliquids should be soluble or dispersible in the solvent. Examples ofsolvents that can be used include alcohols (specific examples includemethanol, ethanol, isopropanol, and butanol), aliphatic hydrocarbons(specific examples include n-hexane, octane, and cyclohexane), aromatichydrocarbons (specific examples include benzene, toluene, and xylene),halogenated hydrocarbons (specific examples include dichloromethane,dichloroethane, carbon tetrachloride, and chlorobenzene), ethers(specific examples include dimethyl ether, diethyl ether,tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycoldimethyl ether, and propylene glycol monomethyl ether), ketones(specific examples include acetone, methyl ethyl ketone, andcyclohexanone), esters (specific examples include ethyl acetate andmethyl acetate), dimethyl formaldehyde, dimethyl formamide, and dimethylsulfoxide. Any one of the solvents listed above may be usedindependently, or any two or more of the solvents listed above may beused in combination. In order to improve workability in production ofthe photosensitive member, a non-halogenated solvent (a solvent otherthan a halogenated hydrocarbon) is preferably used.

Each of the application liquids is prepared by mixing the components inorder to disperse the components in the solvent. Mixing or dispersioncan for example be performed using a bead mill, a roll mill, a ballmill, an attritor, a paint shaker, or an ultrasonic disperser.

Each of the application liquids (the application liquid for chargegenerating layer formation, the application liquid for charge transportlayer formation, or the application liquid for single-layer typephotosensitive layer formation) may for example further contain asurfactant in order to improve dispersibility of the components.

No particular limitations are placed on the method by which each of theapplication liquids (the application liquid for charge generating layerformation, the application liquid for charge transport layer formation,or the application liquid for single-layer type photosensitive layerformation) is applied so long as the method enables uniform applicationof the application liquid on or above the conductive substrate. Examplesof application methods that can be used include dip coating, spraycoating, spin coating, and bar coating.

No particular limitations are placed on the method by which each of theapplication liquids (the application liquid for charge generating layerformation, the application liquid for charge transport layer formation,or the application liquid for single-layer type photosensitive layerformation) is dried so long as the method enables evaporation of asolvent contained in the application liquid. Examples thereof includeheat treatment (hot-air drying) using a high-temperature dryer or areduced pressure dryer. The heat treatment is for example performed forat least 3 minutes and no greater than 120 minutes at a temperature ofat least 40° C. and no greater than 150° C.

The method for producing the photosensitive member may further includeeither or both of an intermediate layer formation process and aprotective layer formation process as necessary. Appropriate knownmethods are selected for the intermediate layer formation process andthe protective layer formation process.

Through the above, the photosensitive member containing the benzidinederivative according to the present embodiment has been described.Through the benzidine derivative according to the present embodiment,crystallization in the photosensitive layer can be inhibited andelectrical properties of the photosensitive member can be improved.

EXAMPLES

The following provides more specific description of the presentdisclosure through use of Examples. However, the present disclosure isnot in any way limited by the scope of the Examples.

<1. Photosensitive Member Materials>

A hole transport material and a charge generating material describedbelow were prepared as materials for forming a charge generating layerand a charge transport layer of a multi-layer photosensitive member. Ahole transport material, a charge generating material, and an electrontransport material described below were prepared as materials forforming a single-layer type photosensitive layer of a single-layerphotosensitive member.

<1-1. Hole Transport Material>

The benzidine derivatives HT-1 to HT-6 described in the embodiment wereprepared as hole transport materials. The benzidine derivatives HT-1 toHT-6 were synthesized according to the methods described below.

<1-1-1. Synthesis of Benzidine Derivative HT-1>

The benzidine derivative HT-1 described in the embodiment wassynthesized through reactions represented by schemes (R-7) to (R-12)shown below. Hereinafter, the reactions represented by the schemes (R-7)to (R-12) may be referred to as reactions R-7 to R-12.

In the reaction R-7, the compound 2a was caused to react with triethylphosphite to give the compound 3a. More specifically, the compound 2a(16.1 g, 0.10 mol) and triethyl phosphite (25.0 g, 0.15 mol) were addedinto a 200 mL flask. The flask contents were stirred at 180° C. for 8hours and subsequently cooled to room temperature. Next, unreactedtriethyl phosphite in the flask contents was evaporated under reducedpressure. Through the above, the compound 3a (mass yield 24.1 g,percentage yield 92 mol %) was obtained as a white liquid.

Next, in the reaction R-8, the compound 3a was caused to react with thecompound 4 to give the compound 5a. The reaction R-8 was a Wittigreaction. More specifically, the compound 3a (13.0 g, 0.05 mol) obtainedthrough the reaction R-7 was added into a 500 mL two-necked flask at 0°C. Air in the flask was replaced with argon gas. Next, driedtetrahydrofuran (100 mL) and a solution of the compound 4 (35.0 g, 0.27mol) in dried tetrahydrofuran (300mL) were added into the flask. Theflask contents were stirred for 30 minutes. Next, 28% sodium methoxide(9.3 g, 0.05 mol) was added into the flask. The flask contents werestirred at room temperature for 12 hours. The flask contents were pouredinto ion exchanged water, and extraction was performed using toluene. Aresultant organic layer was washed five times using ion exchanged waterand dried using anhydrous sodium sulfate. Next, the solvent contained inthe organic layer was evaporated to leave a residue. The resultantresidue was purified using a mixture of toluene (20 mL) and methanol(100 mL). Through the above, the compound 5a (mass yield 3.6 g,percentage yield 30 mol %) was obtained as white crystals.

In the reaction R-9, the compound 6b was caused to react with triethylphosphite to give the compound 7b. More specifically, the compound 6b(15.3 g, 0.100 mol) and triethyl phosphite (25.0 g, 0.150 mol) wereadded into a 200 mL flask. The flask contents were stirred at 180° C.for 8 hours and subsequently cooled to room temperature. Next, unreactedtriethyl phosphite in the flask contents was evaporated under reducedpressure. Through the above, the compound 7b (mass yield 23.2 g,percentage yield 91 mol %) was obtained as a white liquid.

Next, in the reaction R-10, the compound 7b was caused to react with thecompound 5a to give the compound 8b. The reaction R-10 was a Wittigreaction. More specifically, the compound 7b (12.8 g, 0.05 mol) obtainedthrough the reaction R-9 was added into a 500 mL two-necked flask at 0°C. Air in the flask was replaced with argon gas. Next, driedtetrahydrofuran (100 mL) and 28% sodium methoxide (9.3 g, 0.05 mol) wereadded into the flask. The flask contents were stirred for 30 minutes.Next, a solution of the compound 5a (12.2 g, 0.05 mol) obtained throughthe reaction R-8 in dried tetrahydrofuran (300 mL) was added into theflask. The flask contents were stirred at room temperature for 12 hours.The flask contents were poured into ion exchanged water, and extractionwas performed using toluene. A resultant organic layer was washed fivetimes using ion exchanged water and dried using anhydrous sodiumsulfate. Next, the solvent contained in the organic layer was evaporatedto leave a residue. The resultant residue was purified using a mixtureof toluene (20 mL) and methanol (100 mL). Through the above, thecompound 8b (mass yield 15.3 g, percentage yield 89 mol %) was obtainedas white crystals.

Next, in the reaction R-11, the compound 9a was caused to react with thecompound 10a to give the compound ha. The reaction R-11 was a couplingreaction. More specifically, the compound 10a (dichlorobiphenyl, 5.6 g,0.025 mol), tricyclohexylphosphine (0.066 g, 0.00019 mol),tris(dibenzylideneacetone)dipalladium(0) (0.086 g, 0.000094 mol), sodiumtert-butoxide (7.7 g, 0.08 mol), the compound 9a (6.8 g, 0.05 mol), anddistilled o-xylene (500 mL) were added into a three-necked flask. Air inthe flask was replaced with argon gas. Next, the flask contents werestirred at 120° C. for 5 hours and subsequently cooled to roomtemperature. The flask contents were washed three times using ionexchanged water to obtain an organic layer. Anhydrous sodium sulfate andactivated clay were added to the organic layer to perform drying andadsorption treatment of the organic layer. After drying and adsorptiontreatment, the organic layer was subjected to reduced pressureevaporation in order to remove o-xylene. Through the above, a residuewas obtained. The resultant residue was purified using chloroform andhexane (at a volume ratio of 1:1). Through the above, the compound ha(mass yield 7.5 g, percentage yield 71 mol %) was obtained as a solid.

Next, in the reaction R-12, the compound ha was caused to react with thecompound 8b to give the benzidine derivative HT-1. The reaction R-12 wasa coupling reaction. More specifically, the compound ha (10.5 g, 0.025mol) obtained through the reaction R-11, tricyclohexylphosphine (0.066g, 0.00019 mol), tris(dibenzylideneacetone)dipalladium(0) (0.086 g,0.000094 mol), sodium tert-butoxide (7.7 g, 0.08 mol), the compound 8b(17.0 g, 0.05 mol) obtained through the reaction R-10, and distilledo-xylene (500 mL) were added into a three-necked flask. Air in the flaskwas replaced with argon gas. Next, the flask contents were stirred at120° C. for 5 hours and subsequently cooled to room temperature. Theflask contents were washed three times using ion exchanged water toobtain an organic layer. Anhydrous sodium sulfate and activated claywere added to the organic layer to perform drying and adsorptiontreatment of the organic layer. After drying and adsorption treatment,the organic layer was subjected to reduced pressure evaporation in orderto remove o-xylene. Through the above, a residue was obtained. Theresultant residue was purified by silica gel column chromatography usingchloroform and hexane (at a volume ratio of 1:1) as a developingsolvent. Through the above, the benzidine derivative HT-1 (mass yield17.2 g, percentage yield 67 mol %) was obtained.

<1-1-2. Synthesis of Benzidine Derivatives HT-2 to HT-6>

The benzidine derivatives HT-2 to HT-6 described in the embodiment weresynthesized in the same manner as in the synthesis of the benzidinederivative HT-1 except the following changes. The number of moles ofeach of raw materials used in the synthesis of the benzidine derivativesHT-2 to HT-6 was the same as the number of moles of the correspondingraw material used in the synthesis of the benzidine derivative HT-1.

The raw materials shown in Table 1 (compounds 9a, 9b, 9c, 9d, and 9e)were used in the reaction R-11 in the synthesis of the benzidinederivatives HT-2 to HT-6, whereas the compound 9a was used in thesynthesis of the benzidine derivative HT-1. As a result, reactionproducts shown in Table 1 (compounds 11a, 11b, 11c, 11d, and 11e) wereobtained through the reaction R-11. The percentage yield of eachreaction product obtained through the reaction R-11 is shown in Table 1.

The raw materials shown in Table 1 (compounds 11a, 11b, 11c, 11d, and11e) were used in the reaction R-12 in the synthesis of the benzidinederivatives HT-2 to HT-6, whereas the compound 11a was used in thesynthesis of the benzidine derivative HT-1. Furthermore, the rawmaterials shown in Table 1 (compounds 8a, 8b, and 8c) were used in thereaction R-12 in the synthesis of the benzidine derivatives HT-2 toHT-6, whereas the compound 8b was used in the synthesis of the benzidinederivative HT-1. As a result, the benzidine derivatives HT-2 to HT-6were obtained through the reaction R-12, rather than the benzidinederivative HT-1. The percentage yield of each of the benzidinederivatives HT-2 to HT-6 obtained through the reaction R-12 is shown inTable 1.

The compounds 9a, 9b, 9c, 9d, 9e, 11a, 11b, 11c, 11d, lie, 8a, 8b, and8c in Table 1 are respectively represented by chemical formulae (9a),(9b), (9c), (9d), (9e), (11a), (11b), (11c), (11d), (11e), (8a), (8b),and (8c) shown below.

TABLE 1 Reaction R-11 Reaction R-12 Raw Reac- Raw Raw Reac- Benzidinemate- tion Yield mate- mate- tion Yield derivative rial product [mol %]rial rial product [mol %] HT-1 9a 11a 71 11a 8b HT-1 67 HT-2 9a 11a 7111a 8a HT-2 70 HT-3 9b 11b 70 11b 8a HT-3 62 HT-4 9c 11c 72 11c 8c HT-465 HT-5 9d 11d 65 11d 8b HT-5 65 HT-6 9e 11e 60 11e 8a HT-6 60

The raw materials (compounds 8a and 8c) used in the reaction R-12 weresynthesized in the same manner as in the synthesis of the compound 8bexcept the following changes. The raw material used in the reaction R-9was changed from the compound 6b to the raw material shown in Table 2(compound 6a or 6c). As a result, a reaction product shown in Table 2(compound 7a or 7c) was obtained through the reaction R-9, rather thanthe compound 7b. The percentage yield of each reaction product obtainedthrough the reaction R-9 is shown in Table 2. Next, the raw materialused in the reaction R-10 was changed from the compound 7b used in thesynthesis of the compound 8b to the raw material shown in Table 2(compound 7a or 7c). As a result, a reaction product shown in Table 2(compound 8a or 8c) was obtained through the reaction R-10, rather thanthe compound 8b. The percentage yield of each reaction product obtainedthrough the reaction R-10 is shown in Table 2.

The compounds 6a, 6b, 6c, 7a, 7b, and 7c in Table 2 are respectivelyrepresented by the chemical formulae (6a), (6b), (6c), (7a), (7b), and(7c).

TABLE 2 Reaction R-9 Reaction R-10 Raw material Raw Reac- Raw Reac- ofReaction mate- tion Yield mate- tion Yield R-12 rial product [mol %]rial product [mol %] 8b 6b 7b 91 7b 8b 89 8a 6a 7a 90 7a 8a 85 8c 6c 7c85 7c 8c 82

Next, the synthesized benzidine derivatives HT-2 and HT-3 were analyzedusing a ¹H-NMR (proton nuclear magnetic resonance) spectrometer. Themagnetic field strength was set to 300 MHz. Deuterated chloroform(CDCl₃) was used as a solvent. Tetramethylsilane (TMS) was used as aninternal standard. FIG. 1 shows a ¹H-NMR spectrum for the benzidinederivative HT-2 that was measured. Chemical shifts thereof are shownbelow. FIG. 2 shows a ¹H-NMR spectrum for the benzidine derivative HT-3that was measured. Chemical shifts thereof are shown below. The ¹H-NMRspectra and the chemical shifts were used to confirm that the benzidinederivatives HT-2 and HT-3 had structures represented by the chemicalformulae (HT-2) and (HT-3), respectively.

-   Benzidine derivative HT-2: ¹H-NMR (300 MHz, CDCl₃) δ 1.0 (t, 6H),    2.1 (s, 6H), 2.4 (q, 4H), 6.9-7.7 (m, 48H).-   Benzidine derivative HT-3: ¹H-NMR (300 MHz, CDCl₃) δ 2.3 (s, 6H),    6.6-7.4 (m, 50H).

<1-1-3. Preparation of Benzidine Derivatives HT-A and HT-B>

Benzidine derivatives represented by chemical formulae (HT-A) and (HT-B)shown below were also prepared. Hereinafter, the benzidine derivativesrepresented by the chemical formulae (HT-A) and (HT-B) may be referredto as benzidine derivatives HT-A and HT-B, respectively.

<1-2. Charge Generating Material>

Compounds CG-1X and CG-2Y were prepared as charge generating materials.The compound CG-1X was metal-free phthalocyanine represented by thechemical formula (CG-1) described in the embodiment. The compound CG-1Xhad an X-form crystalline structure.

The compound CG-2Y was titanyl phthalocyanine represented by thechemical formula (CG-2) described in the embodiment. The compound CG-2Yhad a Y-form crystalline structure.

<1-3. Electron Transport Material>

The compounds ET-1 and ET-3 described in the embodiment were prepared aselectron transport materials to be contained in single-layer typephotosensitive layers of single-layer photosensitive members.

<2. Multi-Layer Photosensitive Member Production>

Multi-layer photosensitive members A-1 to A-6 and B-1 to B-2 wereproduced using the above-described materials for photosensitive layerformation.

<2-1. Production of Multi-Layer Photosensitive Member A-1>

First, surface-treated titanium oxide (“test sample SMT-02”, product ofTayca Corporation, number average primary particle size: 10 nm) wasprepared. The surface-treated titanium oxide was prepared as describedbelow. Titanium oxide was surface-treated using alumina and silica. Thetitanium oxide surface-treated with alumina and silica was furthersurface-treated using methyl hydrogen polysiloxane during wetdispersion.

Next, an application liquid for undercoat layer formation was prepared.More specifically, the surface-treated titanium oxide (2.8 parts bymass), copolyamide resin (“DAIAMID X4685”, product of Daicel-EvonikLtd., 1 part by mass), ethanol (10 parts by mass) as a solvent, andbutanol (2 parts by mass) as a solvent were added into a vessel. Thevessel contents were mixed for 5 hours using a bead mill in order todisperse the materials in the mixed solvent. Through the above, anapplication liquid for undercoat layer formation was obtained.

Next, an undercoat layer was formed. More specifically, the resultantapplication liquid for undercoat layer formation was filtered using afilter having a pore size of 5 μm. Next, the application liquid forundercoat layer formation was applied to a surface of a conductivesubstrate—an aluminum drum-shaped support (diameter: 30 mm, totallength: 238.5 mm)—by dip coating. Next, the applied application liquidfor undercoat layer formation was heated at 130° C. for 30 minutes.Through the above, an undercoat layer (film thickness: 1.5 μm) wasformed on the conductive substrate.

Next, an application liquid for charge generating layer formation wasprepared. More specifically, the compound CG-2Y (1 part by mass) as acharge generating material, polyvinyl butyral resin (“Denka Butyral#6000EP”, product of Denka Company Limited, 1 part by mass) as a baseresin, propylene glycol monomethyl ether (40 parts by mass) as adispersion medium, and tetrahydrofuran (40 parts by mass) as adispersion medium were added into a vessel. The vessel contents weremixed for 2 hours using a bead mill in order to disperse the materialsin the mixed dispersion medium. Through the above, an application liquidfor charge generating layer formation was obtained. Next, the resultantapplication liquid for charge generating layer formation was filteredusing a filter having a pore size of 3 μm. Thereafter, the applicationliquid for charge generating layer formation was applied to theconductive substrate having the undercoat layer by dip coating. Next,the applied application liquid for charge generating layer formation wasdried at 50° C. for 5 minutes. Through the above process, a chargegenerating layer (film thickness: 0.3 μm) was formed on the undercoatlayer.

Next, an application liquid for charge transport layer formation wasprepared. More specifically, the benzidine derivative HT-1 (70 parts bymass) as a hole transport material, bisphenol Z-form polycarbonate resin(“Panlite (registered Japanese trademark) TS-2050”, product of TeijinLimited, viscosity average molecular weight: 50,000, 100 parts by mass)as a binder resin, BHT (di(tert-butyl)p-cresol, 5 parts by mass) as anadditive, tetrahydrofuran (430 parts by mass) as a solvent, and toluene(430 parts by mass) as a solvent were added into a vessel. The vesselcontents were mixed in order to dissolve the materials in the mixedsolvent. Through the above, an application liquid for charge transportlayer formation was obtained. Next, the resultant application liquid forcharge transport layer formation was applied to the conductive substratehaving the undercoat layer and the charge generating layer in the samemanner as in the application of the application liquid for chargegenerating layer formation. Next, the applied application liquid forcharge transport layer formation was dried at 130° C. for 30 minutes.Through the above process, a charge transport layer (film thickness: 20μm) was formed on the charge generating layer. As a result, themulti-layer photosensitive member A-1 was obtained.

<2-2. Production of Multi-Layer Photosensitive Members A-2 to A-6 andB-1 to B-2>

The multi-layer photosensitive members A-2 to A-6 and B-1 to B-2 wereproduced in the same manner as in the production of the multi-layerphotosensitive member A-1 except the following changes. The benzidinederivative HT-1 used as the hole transport material in the production ofthe multi-layer photosensitive member A-1 was changed to each of thehole transport materials shown in Table 3.

<3. Single-Layer Photosensitive Member Production>

The materials for photosensitive layer formation were used to producesingle-layer photosensitive members C-1 to C-9 and D-1 to D-6.

<3-1. Production of Single-Layer Photosensitive Member C-1>

The compound CG-1X (5 parts by mass) as a charge generating material,the benzidine derivative HT-1 (80 parts by mass) as a hole transportmaterial, the compound ET-1 (50 parts by mass) as an electron transportmaterial, bisphenol Z-form polycarbonate resin (“Panlite (registeredJapanese trademark) TS-2050”, product of Teijin Limited, viscosityaverage molecular weight: 50,000, 100 parts by mass) as a binder resin,and tetrahydrofuran (800 parts by mass) as a solvent were added into avessel. The vessel contents were mixed for 50 hours using a ball mill inorder to disperse the materials in the solvent. Through the above, anapplication liquid for single-layer type photosensitive layer formationwas obtained. The application liquid for single-layer typephotosensitive layer formation was applied to a conductive substrate—analuminum drum-shaped support (diameter: 30 mm, total length: 238.5mm)—by dip coating. The applied application liquid for single-layer typephotosensitive layer formation was hot-air dried at 100° C. for 30minutes. Through the above, a single-layer type photosensitive layer(film thickness: 25 μm) was formed on the conductive substrate. As aresult, the single-layer photosensitive member C-1 was obtained.

<3-2. Production of Single-Layer Photosensitive Members C-2 to C-9 andD-1 to D-6>

The single-layer photosensitive members C-2 to C-9 and D-1 to D-6 wereproduced in the same manner as in the production of the single-layerphotosensitive member C-1 except the following changes. The compoundCG-1X used as the charge generating material in the production of thesingle-layer photosensitive member C-1 was changed to each of the chargegenerating materials shown in Table 4. The benzidine derivative HT-1used as the hole transport material in the production of thesingle-layer photosensitive member C-1 was changed to each of the holetransport materials shown in Table 4. The compound ET-1 used as theelectron transport material in the production of the single-layerphotosensitive member C-1 was changed to each of the electron transportmaterials shown in Table 4.

<4. Evaluation of Multi-Layer Photosensitive Member ElectricalProperties>

With respect to each of the multi-layer photosensitive members A-1 toA-6 and B-1 to B-2 produced as described above, electrical properties ofthe photosensitive member were evaluated. The evaluation of theelectrical properties was performed under environmental conditions of23° C. and 60% RH. First, the surface of the multi-layer photosensitivemember was charged to a negative polarity using a drum sensitivity testdevice (product of Gen-Tech, Inc.). Charging conditions were amulti-layer photosensitive member rotation speed of 31 rpm and an inflowcurrent of −8 μA. The surface potential of the multi-layerphotosensitive member was measured immediately after charging. The thusmeasured surface potential of the multi-layer photosensitive member wastaken to be an initial potential (V₀, unit: V). Next, a band pass filterwas used to obtain monochromatic light (wavelength: 780 nm, half-width:20 nm, light intensity: 0.4 μJ/cm²) from white light emitted by ahalogen lamp. The obtained monochromatic light was irradiated onto thesurface of the multi-layer photosensitive member. The surface potentialof the multi-layer photosensitive member was measured once 0.5 secondshad elapsed after completion of the irradiation. The measured surfacepotential was taken to be a residual potential (V_(L), unit: V). Theinitial electric potential (V₀) and the residual potential (V_(L)) ofthe multi-layer photosensitive members that were measured are shown inTable 3. It should be noted that a residual potential (V_(L)) having asmall absolute value indicates excellent electrical properties.

<5. Evaluation of Single-Layer Photosensitive Member ElectricalProperties>

With respect to each of the single-layer photosensitive members C-1 toC-9 and D-1 to D-6 produced as described above, electrical properties ofthe photosensitive member were evaluated. The evaluation of theelectrical properties was performed under environmental conditions of23° C. and 60% RH. First, the surface of the single-layer photosensitivemember was charged to a positive polarity using a drum sensitivity testdevice (product of Gen-Tech, Inc.). Charging conditions were asingle-layer photosensitive member rotation speed of 31 rpm and aninflow current of +8 μA. The surface potential of the single-layerphotosensitive member was measured immediately after charging. The thusmeasured surface potential of the single-layer photosensitive member wastaken to be an initial potential (V₀, unit: V). Next, a band pass filterwas used to obtain monochromatic light (wavelength: 780 nm, half-width:20 nm, light intensity: 1.5 μJ/cm²) from white light emitted by ahalogen lamp. The obtained monochromatic light was irradiated onto thesurface of the single-layer photosensitive member. The surface potentialof the single-layer photosensitive member was measured once 0.5 secondshad elapsed after completion of the irradiation. The measured surfacepotential was taken to be a residual potential (V_(L), unit: V). Theinitial electric potential (V₀) and the residual potential (V_(L)) ofthe single-layer photosensitive members that were measured are shown inTable 4. It should be noted that a residual potential (V_(L)) having asmall absolute value indicates excellent electrical properties.

<6. Crystallization Resistance Evaluation>

With respect to each of the multi-layer photosensitive members A-1 toA-6 and B-1 to B-2, and each of the single-layer photosensitive membersC-1 to C-9 and D-1 to D-6, the entire surface region of thephotosensitive member (photosensitive layer) was observed using unaidedeyes. Through the above observation, it was confirmed whether or not acrystallized portion was present in the photosensitive layer. Withrespect to each of the multi-layer photosensitive members and thesingle-layer photosensitive members, photosensitive layercrystallization resistance of the photosensitive member was evaluatedbased on the confirmation result in accordance with the followingevaluation standard. Results of the photosensitive layer crystallizationresistance are shown in Tables 3 and 4.

-   (Crystallization Resistance Evaluation Standard)-   G (Good): No crystallized portion observed-   P (Poor): Crystallized portion slightly observed-   PP (Particularly Poor): Crystallized portion observed

The results of the evaluations of electrical properties andcrystallization resistance of the multi-layer photosensitive members areshown in Table 3. The results of the evaluations of electricalproperties and crystallization resistance of the single-layerphotosensitive members are shown in Table 4. In Tables 3 and 4, CGM,HTM, ETM, V₀, and V_(L) represent charge generating material, holetransport material, electron transport material, initial electricpotential, and residual potential, respectively. With respect to each ofthe multi-layer photosensitive member B-1 and the single-layerphotosensitive members D-1 to D-6, the photosensitive member could notbe charged due to crystallization in the photosensitive layer, andtherefore the initial electric potential (V₀) and the residual potential(V_(L)) were unmeasurable.

TABLE 3 Multi-layer Electrical properties Crystallization photosensitiveV₀ V_(L) resistance member HTM (V) (V) Evaluation Example 1 A-1 HT-1−700 −75 G Example 2 A-2 HT-2 −700 −82 G Example 3 A-3 HT-3 −700 −85 GExample 4 A-4 HT-4 −700 −94 G Example 5 A-5 HT-5 −700 −80 G Example 6A-6 HT-6 −700 −86 G Comparative B-1 HT-A Unmeasurable Unmeasurable PPExample 1 Comparative B-2 HT-B −700 −122  P Example 2

TABLE 4 Single-layer Electrical properties Crystallizationphotosensitive V₀ V_(L) resistance member CGM HTM ETM (V) (V) EvaluationExample 7 C-1 CG-1X HT-1 ET-1 +698 +110 G Example 8 C-2 CG-1X HT-1 ET-3+700 +114 G Example 9 C-3 CG-2Y HT-1 ET-3 +700 +106 G Example 10 C-4CG-1X HT-2 ET-1 +700 +115 G Example 11 C-5 CG-1X HT-2 ET-3 +699 +117 GExample 12 C-6 CG-2Y HT-2 ET-3 +699 +111 G Example 13 C-7 CG-1X HT-3ET-1 +700 +114 G Example 14 C-8 CG-1X HT-3 ET-3 +699 +117 G Example 15C-9 CG-2Y HT-3 ET-3 +700 +110 G Comparative D-1 CG-1X HT-A ET-1Unmeasurable Unmeasurable PP Example 3 Comparative D-2 CG-1X HT-A ET-3Unmeasurable Unmeasurable PP Example 4 Comparative D-3 CG-2Y HT-A ET-3Unmeasurable Unmeasurable PP Example 5 Comparative D-4 CG-1X HT-B ET-1Unmeasurable Unmeasurable PP Example 6 Comparative D-5 CG-1X HT-B ET-3Unmeasurable Unmeasurable PP Example 7 Comparative D-6 CG-2Y HT-B ET-3Unmeasurable Unmeasurable PP Example 8

The photosensitive layer of each of the multi-layer photosensitivemembers A-1 to A-6 and the single-layer photosensitive members C-1 toC-9 contained the benzidine derivative 1 (more specifically, any of thebenzidine derivatives HT-1 to HT-6) as a hole transport material.Consequently, as is clear from Tables 3 and 4, these photosensitivemembers were evaluated as good in terms of the photosensitive layercrystallization resistance, and crystallization was inhibited in thephotosensitive layers thereof. Furthermore, these photosensitive membershad a residual potential (V_(L)) with a small absolute value and wereexcellent in electrical properties.

On the other hand, the photosensitive layer of each of the multi-layerphotosensitive members B-1 to B-2 and the single-layer photosensitivemembers D-1 to D-6 did not contain the benzidine derivative 1 as a holetransport material. Consequently, as is clear from Tables 3 and 4, thesephotosensitive members were evaluated as poor or particularly poor interms of the photosensitive layer crystallization resistance, andcrystallization was observed in the photosensitive layers thereof.Furthermore, these photosensitive members had a residual potential(V_(L)) with a large absolute value or could not be charged due tocrystallization in the photosensitive layers thereof.

The evaluation results have proved that the benzidine derivative 1, whencontained in a photosensitive layer of a photosensitive member, caninhibit crystallization in the photosensitive layer and improveelectrical properties of the photosensitive member. The evaluationresults have also proved that a photosensitive member including aphotosensitive layer containing the benzidine derivative 1 can inhibitcrystallization of the photosensitive layer and have excellentelectrical properties.

What is claimed is:
 1. An electrophotographic photosensitive membercomprising a conductive substrate and a photosensitive layer, whereinthe photosensitive layer contains at least a charge generating materialand a benzidine derivative represented by general formula (1) shownbelow as a hole transport material,

wherein in the general formula (1), R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉,and R₁₀ each represent, independently of one another, a hydrogen atom, ahalogen atom, an optionally substituted alkyl group having a carbonnumber of at least 1 and no greater than 6, an optionally substitutedalkoxy group having a carbon number of at least 1 and no greater than 6,or an optionally substituted aryl group having a carbon number of atleast 6 and no greater than 14, and n represents an integer of at least0 and no greater than
 2. 2. The electrophotographic photosensitivemember according to claim 1, comprising, as the photosensitive layer: acharge generating layer containing the charge generating material and acharge transport layer containing the hole transport material; or asingle-layer type photosensitive layer containing the charge generatingmaterial and the hole transport material, wherein the charge generatingmaterial is titanyl phthalocyanine having a Y-form crystal structure. 3.The electrophotographic photosensitive member according to claim 1,wherein the photosensitive layer is a single-layer type photosensitivelayer, the single-layer type photosensitive layer contains the chargegenerating material, the hole transport material, and an electrontransport material, and the electron transport material is a compoundrepresented by general formula (12) shown below

where in the general formula (12), R₁₁, R₁₂, R₁₃, and R₁₄ eachrepresent, independently of one another, a hydrogen atom, a cyano group,an optionally substituted alkyl group, an optionally substituted alkenylgroup, an optionally substituted alkoxy group, an optionally substitutedalkoxycarbonyl group, an optionally substituted aryl group, or anoptionally substituted heterocyclic group.
 4. The electrophotographicphotosensitive member according to claim 1, wherein in the generalformula (1), R₆, R₇, R₈, R₉, and R₁₀ each represent a hydrogen atom. 5.The electrophotographic photosensitive member according to claim 1,wherein in the general formula (1), n represents 1 or
 2. 6. Theelectrophotographic photosensitive member according to claim 1, whereinin the general formula (1), R₁, R₂, R₃, R₄, and R₅ each represent,independently of one another, a hydrogen atom, an alkyl group having acarbon number of at least 1 and no greater than 6 and optionally havingan aryl group having a carbon number of at least 6 and no greater than14, or an aryl group having a carbon number of at least 6 and no greaterthan 14, R₆, R₇, R₈, R₉, and R₁₀ each represent, independently of oneanother, a hydrogen atom or an alkoxy group having a carbon number of atleast 1 and no greater than 6, and n represents 0 or
 1. 7. Theelectrophotographic photosensitive member according to claim 1, whereinthe benzidine derivative represented by the general formula (1) is abenzidine derivative represented by chemical formula (HT-1), (HT-2),(HT-3), (HT-4), (HT-5), or (HT-6) shown below